In many optical and electro-optical systems (e.g., computer systems, programmable electronic systems, telecommunication switching systems, control systems, and so forth) the reliable physical passing of multiple optical fibers through the walls of a package (e.g., a rectangular enclosure with one or more components) is desired, where the fibers transition between the inside and outside of a package.
Such packages are typically populated with components that are disposed upon a plane. For instance, a planar waveguide circuit may be formed on the surface of a section of a silicon wafer, and this surface is the nominal plane of this optical component. The optical components are typically placed within the package so that the planes of the optical components are parallel to the larger-area top and bottom sides of the package, and the components are spaced away from the sides along the height of the package.
One solution for physically routing one or more optical fibers through a wall of a package is to bundle the optical fibers into a cable, e.g., conventionally manufactured lines having a diameter, and route the optical fiber cable through a package wall opening. Another solution for physically routing one or more optical fibers through a wall of a package is to bundle the optical fibers into flat ribbons, and route the flat ribbons through package wall openings in a horizontal orientation. The ribbon orientation is considered to be horizontal if the plane of the ribbon is parallel to the planar waveguide circuit inside the package enclosure.
Additionally, for a typical installation of fiber optic-connected component in such a package, the fibers must be bent in order to connect to other components in the installation. In practice, fiber ribbons are bent only out of the plane of the ribbon. The other components are typically displaced primarily in the plane parallel to the bottom of the package, and it is desirable to route the fibers nominally in that same plane. For a ribbon of optical fibers in a horizontal orientation, the ribbon must frequently be twisted 90 degrees in orientation to rotate the plane of the fibers perpendicular to the plane of the installation. This rotation will then provide the desired ability to physically route the ribbon parallel to the plane of the installation. A very tightly twisted ribbon puts extra stress on the optical fibers and the connection points of the optical fibers. There are physical limitations on how tightly the ribbon can be twisted and how small the bend radius of curvature of the ribbon can be, since twists and bends increase the optical loss along the length of the optical fibers. Bends and twists typically require several millimeters to a few centimeters of fiber length to assure low loss and acceptably low stress. These limitations on the ribbon twisting and bending can also increase the clearance required for the package in the system, and increase the spacing between packages in a system.
FIG. 1 illustrates a top view of a prior art approach for routing optical fibers through a wall of a package in an optical system 100. Optical system 100, as shown in this example, includes six horizontally oriented optical fiber ribbons 102, 103, 104, 105, 106, and 107 routed through the wall 108 of a package 110. Here, the wall 108 must be wide enough for the entry of the three top optical fiber ribbons 102, 104, and 106, and the three bottom optical fiber ribbons 103, 105, and 107. Additional optical fiber ribbons would require a package 110 with a wider wall 108.
It would be desirable to physically route multiple optical fibers in a bundled (e.g., ribbon) configuration through a wall of a package, with a reduction in package size. It would also be desirable to provide an apparatus and method to reduce the stress on optical fibers by reducing the twisting of an optical fiber ribbon physically connected to an external system.